A hybrid vehicle may include an engine, driveline disconnect clutch, a dual mass flywheel, and a driveline integrated starter/generator (DISG) for propelling the hybrid vehicle and for selectively mechanically coupling the engine to the DISG and a transmission. The dual mass flywheel and disconnect clutch may significantly increase driveline inertia. The increased driveline inertia may lead to rougher transmission gear shifts because the inertia may affect transmission input shaft torque during gear shifts. If transmission input shaft torque is too high, a torque disturbance may occur in the driveline that is objectionable to a driver. Therefore, it may be desirable to provide a way of lowering transmission input shaft torque during transmission gear shifting so that a transmission may be smoothly shifted even though the driveline may have a higher inertia.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method, comprising: operating a first group of engine cylinders at a first spark timing retarded from a minimum spark advance for best torque spark timing in response to a gear shift request; and operating a second group of engine cylinders at a second spark timing retarded from the minimum spark advance for best torque spark timing in response to the gear shift request, the second spark timing different from the first spark timing.
By operating two or more cylinder groups at different retarded spark timings, it may be possible to provide the technical result of reducing engine torque so that transmission gear shifting may be improved without operating the engine at conditions where engine torque production is inconsistent. For example, a first group of engine cylinders may be operated at a spark timing retarded from minimum spark timing for best torque (MBT), and a second group of engine cylinders may be operated at a different spark timing retarded from MBT to provide low engine torque with little torque variation. Spark timings where torque variation is increased may be avoided while low torque levels are provided.
The present description may provide several advantages. In particular, the approach may reduce the possibility of driveline degradation by reducing engine torque variation. Further, the approach may improve transmission shift feel. Additionally, the approach may be provided without additional driveline components.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.